If you have not entered into TWRPRecovery Mode, follow the step by step to get into Recovery Mode OnePlus 2 devices. But if the device OnePlus 2 you are logged into TWRPRecovery Mode, now select the Install button.

After that, now navigate to the file UPDATE-SuperSU.zip existing on Internal memory.

If you have selected the file UPDATE-SuperSU.zip, it will display a verification of whether you will do Flashing.

Caution: If you choose to do Flashing, then indirectly you are already receiving a wide variety of risks that will occur on your OnePlus 2 device, such as Bootloop, Brick or other risks.

If you choose to do Flashing, then do Swipe from left to right.

Now you wait for how fast the flashing process is completed. Hopefully you are the lucky ones.

Once the your OnePlus 2 devices restart, you will find the application SuperSU on your OnePlus 2 devices application menu as in the picture below.

Optional: You can also verify if you need it, whether your device is actually already Rooted or not using the application Root Checker.